1. Field of the Invention
The present invention relates to a power controlling system of a display monitor, more particularly, to a power controlling system of a computer monitor and a method thereof, capable of minimizing power consumption for automatically converting a monitor power mode to a power off mode in case that the computer is not used for a certain period of time.
2. Discussion of the Background Art
In general, when a computer is not used for a certain period of time, a power supply circuit in the computer monitor automatically switches a power mode of the computer to a power saving mode until a user presses any key on a keyboard, thereby saving unnecessary power consumption. Recent monitors in the current market mostly have this function.
FIG. 1 is a circuit diagram of a related art power supply circuit of a monitor. The discussion on the related art power supply circuit follows below.
As depicted in FIG. 1, the power supply circuit includes a power input 100 for decompressing input power (AC), a noise filter 110 for filtering noises using output voltage of the power input 100 when a power switch SW1 is turned on, a rectifier 120 for rectifying the output voltage of the noise filter 100 at a bridge diode (BD1) and a condenser C1 and for dividing the rectified voltage Vd through resistors R1 to R3, a power switch 140 for outputting a switching signal by means of voltage division of the rectifier 120, and a voltage output 130 for outputting DC voltage by inducing an output of the rectifier to a secondary side transformer T1 according to an output of the power switch 140.
The problem of the above power supply circuit is that unless the user turns off the power of the monitor, power is continuously supplied to the monitor even when the user is not currently using the computer. As a result, element lifespans in the circuit are dramatically shortened, and thus the reliability of the power supply circuit is lowered.
As an attempt to solve this problem, Korean patent application No. 10-1998-0048370 disclosed an embodiment of a power-saving circuit.
FIG. 2 is a circuit diagram of a power-saving circuit disclosed in the above patent application.
Referring to the drawing, the power-saving circuit includes a rectifier 200 for rectifying and smoothing AC power, a power factor controller 210 for outputting the AC power as power factor-compensated DC voltage, power controllers 220 and 240 for controlling a plurality of transformers, having them output a plurality of different voltages from the applied DC voltage, Micom 270 for controlling the overall power circuit and for outputting a plurality of DPM Display Power Management) control signals in DPM mode, power-saving parts 250 and 260 for outputting a heater power or light emitting signal in response to the DPM control signal, and a main power switch 230 for supplying or switching off power voltage Vcc applied to the power controller 200 under the light emitting signal.
The power-saving circuit satisfies the 2000 IECC, i.e. its power is set at 3 Watt in the power off mode.
However, this type of power-saving circuit does not satisfy the European regulations, Blue Angel, requiring the power consumption in the power off mode to be less than 1 Watt.
This is because even in the off mode, the sub power controller 240, the Micom power (+B7), and the heater power (+B8) continue their operation by an output of the rectifier, by the sub power, and by the first power-saving part, respectively.